This guy know what I was gonna talk about 
Soldering is not hard and it's hard to screw up, you should be fine using google to search how exactly to do it.
Soldering can be tricky for the first timer. Usual mistakes are not having the patience to wait until the iron is hot, and applying way to much solder.
Soldering plugs to wires can be a minor challenge, since you soon find you have at least one hand to little. What you need to do, is use stuff you have around you to make sure the plug do not move once you start soldering. A special soldering-rig is preferable, but those cost money.
But the procedure is simple, as HighMtnSkier said.
1: Cut the plug from the wire. Do so about an inch from where the wire meets the plug. That way you also get rid of the part of the wire that have been bent the most, and thus may be weak.
2: Strip the wire using a carpenters knife, side-cutters or a specialist tool. You don't need to strip more than about half an inch (1-2cm). Inside the wire you will find three conductors, left channel, right channel and ground. Left and right are colour coded, the ground is usually just a metal mesh surrounding the other two conductors. Strip the left and right conductors about 50mm, and twist the ground-mesh into a single strand.
3: Open your old plug to find out what conductor goes where. They are usually colour coded.
4: Thread the new plugs plastic protective jacket onto the wire. You'll do a face-palm later if you forget this...
5: Solder the conductors to their correct places inside the now exposed new plug. Easiest way is to melt a tiny bit of solder on the tip of the iron, thread the conductor to the little nook in the plug where it is supposed to be attached, and then touch it with the tip of the soldering iron until a small amount of solder have transferred. Let cool for a few seconds whilst you rinse the iron. Repeat with the other conductor, and finally solder the ground conductor to the metal protector.
6: Everything in place, and have cooled a bit, just screw or click the plastic protective jacket (depends on type) over the exposed plug, and you're done.
Should take 5 minutes or less.
I just love the smell of hot solder in the morning